We have assessed the prevalence of exercise-induced ventricular tachycardia, exercise-induced supraventricular tachycardia and post-exercise hypotension in BLSA volunteers without clinical evidence of heart disease. Out of 925 subjects undergoing maximal treadmill exercise between September, 1977 and December, 1983, 10 subjects (1.2%) developed nonsustained ventricular tachycardia (VT) during or after exercise. Episodes varied in length from 3 to 6 beats and were associated with symptoms. The prevalence of VT was 3.8 % in subjects aged 65 and older. Over a follow-up period averaging 2.0 years, no subject with exercise-induced VT developed syncope, pre-syncope, angina myocardial infarction or sudden death. Exercise-induced supraventricular tachycardia (SVT) occurred in 50 subjects (5.3%). All episodes were paroxysmal atrial tachycardia; heart rate varied from 120 to 250 bpm. Of the 70 episodes of SVT, only 12 were Greater than or equal to 10 beats in length; 4 of these were associated with symptoms. The prevalence of SVT was 12.7% in the 245 subjects Greater than or equal to 65 years old but only 2.7% in those Less than 65 years. An ischemic ST segment response to exercise occurred in 14% of subjects. Hypotension following treadmill exercise, defined by a fall in systolic blood pressure (SBP) at least 20 mm Hg below sitting pre-exercise level to value Less than 90 mm Hg, occurred in 15 subjects (1.7%) with a mean age of 44.2 years. Bradycardia was associated with hypotension in only 3 subjects. When compared with age-matched controls, hypotensive subjects had higher maximal heart rates (183.9 vs 173.1 bpm) but no differences in SBP at submaximal or maximal effort. Post -exercise ST segment abnormalities suggestive of myocardial ischemia occurred in one third of the hypotensive subjects but none of the controls, pLess than.05.